Poling Effect on Pyroelectric Effect in Ferroelectric Thin Films

Ferroelectric thin films offer numerous applications, such as nonvolatile memories, piezoelectric sensors, and actuators. It is also noteworthy that significant pyroelectric and electrocaloric effects have been reported in ferroelectric thin films, providing potential applications to infrared sensors, energy harvesting, and electrocaloric cooling. Electrical poling with DC or AC voltages enhances remanent polarization and piezoelectric coefficient. Although the pyroelectric coefficient also increases with increasing poling voltage [1], its relationship with a degree of poling is not straightforward [2].<br/>Here, we investigate the impact of poling on the pyroelectric effect. In this study, using lead zirconate titanate (PZT) with morphotropic phase boundary composition prepared by sol-gel method, we simultaneously measured the pyroelectric effect and the remanent polarization by varying DC poling time. We measured the pyroelectric current via local AC heating at 220 Hz with a Pt thin film heater stacked on the PZT, and the remanent polarization by applying a triangular pulse at 1 kHz. The results show an increase in both the pyroelectric current and the remanent polarization with increasing DC poling time. With the same poling time, the pyroelectric current increased more rapidly than the remanent polarization did, suggesting the importance of poling in enhancing pyroelectric effects and the significance of direct evaluation of pyroelectric properties.<br/>[1] L. L. Sun et al., Infrared Phys. Technol. 44, 177 (2003).<br/>[2] S. W. Smith et al., Appl. Phys. Lett. 113, 182904 (2018).